1. Field of the Invention
The present invention relates to a blower device including an axial flow fan, which is, for example, used for obtaining an air flow directed to a radiator for an internal combustion engine.
2. Description of Related Art
Known is an axial flow fan for a radiator in an internal combustion engine where the fan has a plurality of circumferentially spaced blades with each blade extending radially. The small axial dimension of the fan necessitates the number of the blades being increased, for example, to seven or more. However, in the prior art, such an increase in the number of blades causes the efficiency to be reduced, due to the fact that seven or more fan blades causes the solidity of the blade, which is a ratio of a chord length of a blade to a blade pitch, to be greatly reduced. Namely, a reduction in the solidity causes the chord length to be highly reduced and this causes a pressure gradient on the surface of the blade to be increased thereby causing air flows to separate from the surface.
Furthermore, the prior art fan generates a large operating noise when the fan is used as a pushing flow type. This is the case when the fan is arranged between a front grill and a heat exchanger such as a condenser in an engine compartment for a vehicle, so that a flow of air is sucked from the grill and pushed to the heat exchanger is created.